The present disclosure, in various exemplary embodiments, relates to electrophotographic imaging members and, more specifically, to layered photoreceptor structures with improved overcoat layers and processes for making the imaging members. For example, one exemplary embodiment relates to a particular overcoat composition for producing a high quality surface finish.
Electrophotographic imaging members, i.e. photoreceptors, typically include a photoconductive layer formed on an electrically conductive substrate. The photoconductive layer is an insulator in the dark so that electric charges can be retained on its surface. Upon exposure to light, the charge is dissipated.
An electrostatic latent image is formed on the photoreceptor by first uniformly depositing an electric charge over the surface of the photoconductive layer by one of the many known means in the art. The photoconductive layer functions as a charge storage capacitor with charge on its free surface and an equal charge of opposite polarity on the conductive substrate. A light image is then projected onto the photoconductive layer. The portions of the layer that are not exposed to light retain their surface charge. After development of the latent image with toner particles to form a toner image, the toner image is usually transferred to a receiving substrate, such as paper.
Imaging members can have a number of different configurations. For example, they can comprise a flexible member, such as a flexible scroll or a belt containing a flexible substrate support. The flexible member belt may be seamed or unseamed. The electrostatographic imaging members can also be a rigid member, such as those utilizing a rigid support substrate drum. Drum imaging members have a rigid cylindrical supporting substrate bearing one or more imaging layers. The use of such small diameter drums or flexible imaging belts places a premium on photoreceptor life.
In certain imaging applications, blades or other flexible members are used to clean film and debris off the surface of a photoreceptor belt. Debris such as carrier beads, toner agglomerates or paper dust, removed from the photoreceptor belt, typically detach from the edge of the blade or flexible member and are captured by a cleaner brush or other component. However, not all debris is removed from the blade. And thus, a portion of the debris remains at the interface of the blade and photoreceptor. As the blade wears, the tip pressure of the blade often decreases resulting in further entrainment of debris along the edge or tip of the blade. Debris trapped along the blade can scratch or otherwise cause abrasive action on the surface of the photoreceptor. If the abrasive action is sufficiently severe, cracking of the outermost surface of the photoreceptor can also occur. The resulting scratches, if sufficiently significant, can cause a variety of printing defects, and can cause unwanted marks in a printed image. Accordingly, there is a need for a strategy to prevent, or at least reduce, the potential for scratch-induced printing defects or in severe cases, cracking of a photoreceptor surface.